Monte Carlo simulations in the grand canonical ensemble, the histogram reweighting technique and finite size scaling are used to study the phase behavior of heteronuclear di ners adsorbed on heterogeneous surfaces. The dimers are composed of A and B type segments. The model with attractive AB and BB nearest-neighbor energy (uAB=uBB=-1) and repulsive AA interactions is considered. The surface is composed of alternating strips of non-interacting and attractive sites arranged on a square lattice. The adsorption isotherms, phase diagrams and critical parameters are estimated. It is shown that surface heterogeneity markedly affects the adsorption and phase behavior of the films. The impact of surface topography on critical characteristics is analyzed. Of special interest is the finding that these systems do not belong to the two-dimensional Ising class of universality.